The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet detection. A camera based on such a material presents an extremely low dark current at room temperature. It can compete with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays for low flux measurements. First, we will present results on focal plane array of 320 × 256 pixels with a pitch of 30 μm. The peak responsivity is tuned from 260 nm to 360 nm in different cameras. All these results are obtained in a standard SWIR supply chaine and with AlGaN Schottky diodes grown on sapphire. We will present here the first attempts to transfer the standard design Schottky photodiodes on from sapphire to silicon substrates. We will show the capability to remove the silicon substrate, to etch the window layer in order to extend the band width to lower wavelength and to maintain the AlGaN membrane integrity.

Hexagonal AlN thin films have been deposited by DC reactive magnetron sputtering at room temperature. For a first set of samples, sputtered AlN films were deposited on silicon Si (100) substrates. For a second set, AlN films were deposited on 200 nm (002) oriented AlN epitaxial layer obtained by Molecular Beam Epitaxy (MBE) on Si (111). X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM) analysis of the synthesized films on Si (100) substrate have shown an amorphous phase close to the interface followed by a nano-crystalline layer exhibiting (100) and (002) orientations of the hexagonal AlN crystalline phase. Finally a relatively well crystallised layer with a single (002) orientation has been observed for the thickest films. This improvement of crystalline quality with film thickness has been consistent with a drastic decrease of the films stress from –1.2 GPa at 300 nm to no stress around 800 nm and even 0.3 GPa tensile stress for 1.5 μm thick film. This behaviour was different when epitaxial AlN was used as substrate. In fact, we have observed thanks to HRTEM images and Selected Area Electron Diffraction (SAED) patterns, that the AlN film deposited on such a substrate exhibits the same crystalline quality and have the same orientation as the AlN epitaxial layer during the first 500 nm of thickness. A further increase of film thickness has caused a decrease on the crystalline quality. The films became polycrystalline while preserving a (002) preferential orientation.

In this review, we report on the use of low pressure plasmas for elaboratingmaterials at the heart of solid polymer fuel cells (SPFC), especially electrodes and themembrane electrolyte. Electrodes are formed using plasma sputtering techniques while theion conducting membranes are built up using plasma polymerization. Fuel cell performance willbe improved by these approaches. The electrode catalyst profile is optimized whilemembrane working temperature is increased and methanol crossover is lowered compared to conventional PEM fuel cells.

Self-organized InAs quantum islands (QIs) were grown in the Stranski-Krastanov regime, by solid source molecular beam epitaxy (SSMBE), on In0.52Al0.48As layer lattice matched to InP(001) substrate. The growth parameters are chosen to produce dot shaped InAs islands as indicated by the photoluminescence (PL) linear polarization which is about 9%. The PL spectrum reveals several resolvable components. PL versus power excitation and photoluminescence excitation (PLE) measurements show clearly that this multi-component spectrum is related to emission from transitions associated to fundamental and related excited states of quantum dots (QDs) having monolayer-height fluctuations. The integrated PL intensities have been measured as a function of temperature in the 8–300 K range. The PL intensity measured at 300K is only 8 times lower than at 8 K, indicating good carrier confinement in these InAs/InAlAs QDs. An enhancement of the PL intensity in the 8–90 K temperature range has been tentatively attributed to the exciton dissociation from the InAlAs barriers which then recombine radiatively in the InAs QDs.

Recent experimental and theoretical studies highlighted the importance of the growing surface structure on the final morphology of GaN. Actually, optimum morphology is achieved by growth in presence of a Ga bilayer adsorbed on the GaN surface. The threshold fluxes limiting the region of the Ga bilayer adsorption have been measured as a function of the GaN substrate temperature, giving rise to a Ga adsorption phase diagram. The Ga flux limiting the regions in the adsorption phase diagram exhibit a linear behavior in an Arrhenius plot. However, both energy activation (about 5 eV) and prefactor (in the 1025 range) are surprinsingly high. These questions were adressed by studying the adsorption/desorption of Ga adatoms and small islands (consisting of 2 and 3 Ga adatoms) on the Ga bilayer surface employing first principle density functional theory calculations. We find a desorption barrier of 2.1 eV and a binding energy between two Ga atoms of approximately 0.3 eV. Using these numbers we derived a simple growth model (based on rate equations). An analysis of the experimental data with the model revealed the origin of the large difference in the activation energies and the unusually large prefactor. We find that the nucleation of the droplets cannot be described by a simple Arrhenius behavior (as commonly assumed to fit experimental data) but that the nucleation energy is temperature dependent.

In this paper, we study the surfactant capability of In for the growth of AlGaN/GaN heterostructures by plasma-assisted molecular beam epitaxy. Growth conditions were determined to have a self-regulated 1×1 In adlayer on AlxGa1-xN (0001). The presence of this In film favors two dimensional growth of AlGaN under stoichiometric conditions, and inhibits the formation of metal droplets on the surface. The quality of these layers was assessed by high resolution X-ray diffraction, atomic force microscopy and photoluminescence.

The only surviving manuscript of the Lord Marshal's Roll (LM) is preserved in the Library of the Society of Antiquaries of London (MS 664, vol. 3, fols 19–25 [Roll 15]; Wagner 1950, 38). The original was no doubt in poor condition when this copy, a Hatton-Dugdale facsimile, was executed c. 1640. Many shields are defective, often showing silver instead of gold (e.g., LM 59, 60, 64, 68, 71, 73, 79, 82, 87, 304; similarly, silver instead of vair, LM 127, 331, 463, 554), omitting charges (LM 58, 90, 103, 434 (see below), 585), and reversing tinctures (LM 322). Other shields are blank and/or bear no caption. In spite of these and other flaws, LM remains one of the most important rolls of arms of the reign of Edward I (1272–1307).2 It is one of the lengthiest rolls of the period—588 entries—and although some captions are garbled, most of the identifying names are quite legible. Also, LM was composed at a time of crisis for Edward I (1294–8) and on the eve of the war against the Scots (1296–1307) to which several later rolls bear witness (Prestwich 1988, 401–35; 469–516).

A comparative study of three thirteenth-century rolls of arms, the Heralds' Roll, the Dering Roll, and the Camden Roll, shows the extent to which the first was copied in the preparation of the other two. Light is also thrown on the way in which heraldic copyists worked and on the identity and nature of early armorial bearings.

The multiplicity of terms used to blazon crosses and the diversity of manners in which they were depicted constitute one of the most confusing aspects of medieval heraldry. Sir William St. John Hope deplored this situation in the following terms:

As regards the cross, heraldic writers have gone mad, and from the few simple crosses of pre-Tudor days there have been evolved scores of fantastic forms for which it would be difficult to find instances outside the heraldry books. In the Glossary of Heraldry, published in 1847, upwards of fifty varieties are enumerated, and there are other modern works in which they exceed two hundred!

A recent survey estimates that there are. today in the six New England states alone well over a million persons of French-Canadian descent, the overwhelming majority of whom understand and speak French natively. At a time when increased and improved knowledge of modern foreign languages is patently needed, this vast pool of native speakers and potential teachers of French constitutes an increasingly valuable linguistic resource. The Franco-American Institute held at Bowdoin College in the summer of 1961 under the terms of the National Defense Education Act sought to exploit more fully in the national interest this New England French resource. The Institute marked the first time in history that an ethnic group was accorded federal support in its struggle to preserve its linguistic heritage—a sharp divergence from official efforts at intensive Americanization following World War I. It was also the first concerted effort made in this country by language teachers of any nationality to come to grips in a realistic way with the problem of teaching the standard form of a language to a group of persons whose second language is non-standard. The central problem faced by the Institute was the unquestioned right of French-Canadian speech to be recognized as a respectable means of communication. All due respect was accorded to this linguistically-sound fact, but the Institute nevertheless took the position that the national interest demands the teaching of standard French in all U. S. schools today.